The present invention relates to exhaust gas recirculation valves for use with internal combustion engines.
Exhaust gas recirculation (EGR) valves capture engine exhaust and recycle at least a portion of that captured exhaust gas into the combustion chamber of the engine to improve combustion. Exhaust gas is used since it is readily available and contains only a small amount of oxygen. Adding the exhaust gas to the air in the combustion chamber has the effect of lowering the combustion temperature below the point at which nitrogen combines with oxygen. Thus, exhaust gas recirculation increases fuel economy and reduces the level of undesirable emissions.
Conventional EGR valves include an actuator and a metering base. The metering base includes a metering chamber having a metering port. The metering chamber has an end that is associated with the intake manifold or intake vacuum of the engine. The metering port is connected to a source of exhaust gas and provides a passageway for the flow of exhaust gas into the metering chamber. An elongate shaft extends contiguously in a longitudinal direction from the actuator, through an orifice in the metering base, into the metering chamber, and to the metering port. A metering poppet, which is a plunger-shaped member, is disposed at the end of the shaft proximate to the metering port. In a default position, the metering poppet abuttingly engages or is disposed within the metering port, thereby sealing the metering port. In this default position, no exhaust gas enters the metering chamber through the metering port. The shaft is reciprocated to displace the metering poppet from engagement with the metering port thereby unsealing the metering port and allowing exhaust gas to flow through the metering port into the metering chamber and into the intake manifold of the engine. Thus, the reciprocal motion of the shaft and metering poppet selectively control the flow of exhaust gas into the intake air stream of the engine.
Automotive engines operate under relatively high exhaust backpressure and pressure pulsations. These conditions of high backpressure and pressure pulsations can interfere with the operation of conventional EGR valves. The high amplitude pulsations can render the EGR valve uncontrollable by interfering with the motion of the shaft as the metering poppet comes into and out of sealing engagement with the metering port. Furthermore, the high amplitude pulsations increase the air loading on the relatively large surface area of the metering poppet. The increased air loading on the metering poppet increases the force necessary to reciprocate the shaft. The actuator must be designed to produce enough force to reciprocate the shaft under these conditions of high-amplitude pressure pulsations and increased air loading on the metering poppet. Thus, the actuator must be designed to produce more power than would be required to reciprocate the shaft absent the pressure pulsations and high back pressure. Automotive manufacturers are continually striving to decrease the cost, size and weight of components in order to conserve valuable and cramped engine compartment space, to decrease vehicle cost, and to decrease the overall weight of vehicles in the interest of fuel economy. An actuator that produces higher force comes with the undesirable consequences of increased size, weight, and cost.
In striving to increase fuel economy, automotive manufacturers have produced engines which are intended to operate using higher proportions of recirculated exhaust gas in their combustion air charge. Some automobile engines are designed to operate with as much as fifteen-percent of their intake air stream composed of recirculated exhaust gas. This demand for a higher flow rate of recirculated exhaust gas, in turn, demands a higher flow rate of exhaust gas through the EGR valve. The demand for a higher flow rate of exhaust gas places a corresponding demand on the actuator of the EGR valve. In order to meet this demand for a higher flow rate, a more powerful actuator typically must be used, thereby incurring the undesirable consequences of an actuator having increased size, weight and cost.
Therefore, what is needed in the art is an EGR valve which is resistant to the pressure pulsations and high backpressure.
Furthermore, what is needed in the art is an EGR valve which produces a high flow rate without requiring a large, high-force actuator.
Moreover, what is needed in the art is an EGR valve having a modular design and construction.
The present invention provides a pressure balancing metering subassembly for use with an actuator of a modular EGR valve.
The invention comprises, in one form thereof, a metering base having a metering port and a metering chamber. An elongate poppet includes a first end normally disposed in sealing engagement with the metering port. The poppet is selectively reciprocated to disengage the first end from sealing engagement with the metering port to thereby fluidly connect the metering port with the metering chamber. Pressure balancing means balance a pressure at the first end of the poppet with a pressure at a second end of the poppet.
An advantage of the present invention is that the effect of backpressure, pressure fluctuations, and pressure differentials upon reciprocation of the poppet is reduced.
Yet another advantage of the present invention is that less force will be required to reciprocate the poppet.
A still further advantage of the present invention is that less power will be required from an actuator to reciprocate the poppet.
An even further advantage of the present invention is that it can be coupled to an actuator to form a modular EGR valve.